i posted a similar thread some time back.. was told that i'd be better off with the propriety flashes.. so not sure..
there are third party brands are like sigma.. suntax.. metz.. to name a few.. i heard lately there's a real cheap singapore-brand for flashes (can't remember the name).. you might want to check them out.. juz visit any of the more renowned camera shops.. =)
go ahead.... at the risk of picture quality and also a more difficult time with the adjustments. Cheaper alternatives have such problems. The other 3rd party flashes which have TTL and such compatability are not cheap either.